Experimental Research on the Waterjet Oscillating Characteristics of Helmholtz Nozzle

Wei Ma ； Tengfei Cai ； Fei Ma

《淡江理工學刊》 22卷1期 (2019/03) Pp. 83-92

https://doi.org/10.6180/jase.201903_22(1).0009

摘要

Helmholtz nozzle is a typical self-resonating waterjet generator, and has been extensively investigated through target hitting experiment. This paper on jet flow state reveals the essential characteristics of Helmholtz nozzle jet by signal analysis method. The flow pressure pulsation signals were directly acquired in the nozzle's cavity. Spectrum analysis was employed to analyze the oscillating characteristics of self-resonating waterjet generated by a series of Helmholtz nozzles with different structures. The noise level was detected using self-resonating waterjet to hit the target under confining pressure and the cavitation effect was investigated through analyzing the noise power spectrum. The experimental results showed that compared with the organ-pipe and conical nozzles, the self-resonating waterjet generated by Helmholtz nozzle had high-frequency pressure oscillation and strong cavitation effects. The Helmholtz nozzle's upper portion determines the resonance frequency. Meanwhile, The upper structure of the Helmholtz nozzle promotes the cavitation generation, and Helmholtz oscillation cavity enhances the cavitation effect of the self-resonating waterjet.

關鍵字

Helmholtz Nozzle ； Self-resonating Waterjet ； Frequency Characteristics ； Cavitation Noise ； Signal Analysis